nicer GUI for special viewpoints:

* added "90 degrees rotation around axis perpendicular to the screen" button
  (+90, or -90 when holding Shift)
* clicking on X,Y,Z buttons with Shift now gets the view "from behind"

little hack for philou: clicking on "Z" while holding "Shift" will cycle
through 90 degrees increments of rotations around the Z-axis

add links to new interactive tutorials

some new examples

link to new gui tutorial about visualizing deformations

getFirstPhysical -> getLastPhysical, so that the coloring gets made according
to the latest physical entity created instead of the first one.

Requested by philou; most interesting when creating physical groups on
existing meshes.

say explictly that LaTeX XXX part output is without text

reverting last change: it's nicer to always have the z axis pointing up

change y,-y to have the axes the same way as for x,-x and z,-z

don't optimize transfinite volumes!

trying to fix the transfinite volume bug introduced by the 'left' and
'alternate' transfinite surface changes made a while ago

fix stat print for pyramids

new shortcuts for alternative x, y, z views (still needs to be completed by dave)

forgot to indent these two

- the fltk m#@!er f*!@ers changed the way FL_CTRL/FL_META shortcuts
are treated on the Mac. This patch forces FL_META (the "Apple key") for
all Ctrl shortcuts in the menu. I think this is the way most people on
Macs would expect the shortcuts to work anyway.

- fix metis readme+configure info

update tetgen to latest version 1.3.4

upgrade triangle to version 1.6

prepare for 1.61

disable applyOptimizationPatterns for now